How to Use a Clinometer Page 1 of 3

How to Use a Clinometer 

DOCUMENT 

1201 

Page 

1 of 3 

Height, slope and 

vertical angle measurements 

made easy! A clinometer can be used to 

measure heights of trees, poles, towers, and buildings. 

You can also use it to measure slopes for preliminary surveying, 

grade work, and site drainage. Vertical angles can be measured as well 

for engineering and surveying projects, satellite and microwave dish installation 

and more. The following pages include instructions for using clinometers in 

various situations. 

43830 Percent and degree scales (±150%, ±90°). Cosines to 45° on back. 

43895 Percent and topographic scales (±150%, ±200’ @ 66’ baseline). Percent/degree 

conversions on back. 

43904 Percent and degree scales with built-in rangefinder, target for 50’, 100’ baselines. 

Cosines to 45° on back. 

43831 Percent and degree scales with built-in light. Cosines to 45° on back. Battery 

included. 

43896 Degree and topographic scales (±90°, ±200’ @ 66’ baseline). Cosines to 45° on 

back. 

43893 Degree and topographic scales with built-in rangefinder, target for 66’, 132’ baselines 

(±90°, ±200’ @ 66’ baseline). 

43897 15m and 20m scales (±35m @ 15m baseline, ±50m @ 20m baseline, respectively). 

20m scale/degree conversions on back. 

43877 15m and 20m scales with built-in rangefinder, target for 14m and 20m baselines. 

(±35m @ 15m baseline, ±50m @ 20m baseline, respectively). 20m 

scale/degree conversions on back. 

43840 Percent and secant scales* (±150%, secant values x 100 – 100 to ±500). 

Percent/degree conversions on back. 

43832 Degree and secant scales (+90°, cosines 0 to 45°). 

Note: Since 43840 and 43832 secant scale clinometers express secant of a slope 

times 100, you should initially divide the clinometer reading by 100 to get the correct 

secant value. For example, a clinometer reading of 110 has a correct secant value of 

1.10. 

*Secant scale clinometer 43840 allows you to determine correct horizontal distances 

and compensate for slope when using the percent scale for height measurements. You 

can also eliminate prism rotation in point sampling. 

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1-800-430-5566 

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1-800-647-5368 

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the phone. 

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orders, visit our web site to place your 

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Forestry Suppliers, Inc. accepts Visa, 

MasterCard and American Express. 

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Jackson, Mississippi 39201 Int’l Sales: (601) 354-3565 e-mail: fsi@forestry-suppliers.com

How to Use a Clinometer 

DETERMINING HEIGHT USING A PERCENT 

SCALE CLINOMETER 

DOCUMENT 

1201 



To acquire height measurements with a percent scale clinometer, stand any convenient horizontal 

baseline distance from an object in which you can see both the top and bottom of the object. 

Then sight the top of the of the object for the top % reading and the bottom of the object for the 

bottom % reading. 

Then follow this simple mathematical formula to calculate the height: 

% to top - % to bottom = total % height 

then 

total % height x horizontal baseline distance = height. 

Note the following examples as they relate to different ground circumstances and horizontal 

baseline distances: 

Height measurements on level ground and above a tree. 

Using the percent scale and horizontal baseline distance convenient for you to see both the top 

and bottom of the tree, follow these simple procedures. Back away from the tree the baseline 

distance. In this example, 80’. Sight the top of the tree and read the % scale (63%). Sight the 

bottom of the tree and read the % scale (-7%). Subtract the bottom reading from the top reading: 

63% -(-7%) = 70%. To obtain tree height, simply multiply this percentage times your horizontal 

baseline distance. 70% x 80’ = 56’ tree height. (See Figure 1.) 

Height measurements on sloping ground and below the tree. 

Using the percent scale and 100’ horizontal baseline (or other baseline convenient for you to 

see both the top and bottom of the tree), follow these simple procedures. When the base of the 

tree is ABOVE eye level, sight the top then sight the base. Subtract the base reading from the 

top reading. This example: 70% - 14% = 56%. Then multiply 56% x 100’ = 56’ (tree height). 

(See Figure 2.) 

When the base of the tree is BELOW eye level, sight the top then sight the base. Subtract the 

bottom reading from the top reading. For example, 

-10% top reading - (-66% bottom reading) = 56%. Then multiply by 100’ (baseline) for a tree 

height of 56’. 

56' 

63% 

-7% 

80' 

Figure 1 

14' 14% 56% 

100' 

Figure 2 

1.05 

B = 1.05 

A = 100' 

C = 95.24' 

Figure 3 

USING A SECANT SCALE CLINOMETER TO DETERMINE: 

Horizontal distance on sloping ground. 

To find an unknown horizontal distance (C), divide the measured 

slope distance (A) by the secant value of the slope (B). This example: 

100 ft. ÷ 1.05 = 95.24 ft. (horizontal distance). (See Figure 3.) 

Correct slope distance for a desired horizontal distance. 

Correct slope distance (C) is determined by multiplying the required horizontal baseline distance 

(A) times the secant value of the slope (B). This example: 100 ft. x 1.05 = 105 ft. (correct slope 

distance). (See Figure 4.) 

B = 1.05 

C = 105' 

A = 100' 

Figure 4 

1.05 




How To Use a Clinometer 

DOCUMENT 

1201 



USING TOPOGRAPHIC & METRIC SCALE 

CLINOMETERS TO MEASURE HEIGHT 

The topographic scale clinometer is designed to measure heights directly in feet when 

using a horizontal baseline of 66’. Take readings the same way described for the percent 

scale clinometer. The topographic scale can also be used at a horizontal baseline of 33’ 

or 132’, but the reading must be halved or doubled, respectively. 

The metric scale clinometer is used much the same as the topographic scale clinometer, 

in that they both read directly when at the horizontal baseline distance prescribed for 

them. The metric scale clinometer reads heights directly in meters. 

CLINOMETER SCALES 

Each clinometer has two scales which are available in the following combinations: 

Percent and Degree, Percent and Topographic, Degree and Topographic, 15m and 20m, 

Percent and Secant, or Degree and Secant. Scales are graduated from 0-90° in 1° units; 

from 0 to 150% in 1% units (0 to 70%) then in 2% units (70% to 150%). Graduations in 

the topo scale are 0 to ±200’ with a 66’ baseline. Scale readings can be estimated to 10 

minutes or 1/5%, when readings are made around the zero level. 

Measuring Slope 

To measure slope, using a percent scale clinometer, sight parallel with the ground (upslope or 

downslope) to a target, aiming at a point on the target that is equal to the height of your eye above 

the ground. 

Clinometer Basics 

How to hold and read a 

clinometer 

Keep both eyes 

open when using a 

clinometer. Use 

the sight eye to 

look through the 

lens at the scales 

while the left eye 

sights alongside the clinometer housing. 

An optical illusion is created and the horizontal 

sighting line will appear to project to 

the side of the clinometer housing. Place 

this sighting line on your target and read 

the scale. 

Which Scale to Use: 

Clinometer Required Clinometer 

Scale Used Baseline Distance Reads In 

Topo 66 feet feet 

15m 15 meters meters 

20m 20 meters meters 

Any distance % of baseline 

Percent in feet, yards, distance you 

or meters 

select 

Important Notice 

The axes of the eyes of some people 

are not parallel, a condition called heterophoria. 

In order to be sure that this 

doesn’t affect the accuracy of readings, 

it is suggested that the operator check 

this possibility as follows: 

Take a reading with both eyes open 

and then close the eye not looking 

directly into the clinometer scales. If 

the reading doesn’t change appreciably, 

there is no disalignment of the eye 

axes, and both eyes can be kept open. 

Should there be a difference in the 

readings, one has to keep the eye not 

looking directly into the clinometer 

scales closed and sight partly past the 

instrument body making use of the 

optical illusion.

How to Use a Clinometer Page 1 of 3

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